1. Field of the Invention
Embodiments of the invention generally relate to electronic device processing, and more particularly, to vapor deposition processes for metal-containing materials and the compositions of the metal-containing materials.
2. Description of the Related Art
The electronic device industry and the semiconductor industry continue to strive for larger production yields while increasing the uniformity of layers deposited on substrates having increasingly larger surface areas. These same factors in combination with new materials also provide higher integration of circuits per unit area on the substrate. As circuit integration increases, the need for greater uniformity and process control regarding layer characteristics rises.
Several areas of fabrication that are constantly improving include the formation of metal gate electrodes and the deposition of contact barrier layers. Gate electrodes have often been made with silicon based materials, but more frequently are made with metallic materials, such as tungsten or cobalt. However, the materials used for gate electrodes have had less than desirable electronic properties. While tantalum materials have been used in semiconductor structures, such as barrier layers, tantalum materials have only been scarcely used for the formation of metal gate electrodes, despite the variety of electronic characteristics available from tantalum materials.
Gate materials layers formed from sputtered tantalum and reactive sputtered tantalum nitride have demonstrated suitable electronic properties. Exemplary properties include high conductivity, high thermal stability, and resistance to diffusion of foreign atoms. Physical vapor deposition (PVD) processes are used to deposit tantalum materials as gate electrodes or in features of small size (e.g., about 90 nm wide) and high aspect ratios of about 5:1.
Advancement in technologies for forming semiconductor structures will now require conformal deposition on the bottom and side walls for work function materials on high k dielectric materials and gate electrodes on work function materials as opposed to the traditionally bottom only deposition approach making PVD undesirable and many CVD processes producing less than desired results. Further, it is believed that PVD processes may have reached a limit at this size and aspect ratio. Also, the variety of compositions for tantalum materials is very limited when using a PVD process.
Attempts have been made to use traditional tantalum precursors found in chemical vapor deposition (CVD) or atomic layer deposition (ALD) processes to deposit tantalum materials. Multiple CVD and ALD processes are anticipated to be used in the next generation technology of 45 nm wide features having aspect ratios of about 10:1 or greater. Also, ALD processes more easily deposit tantalum materials on features containing undercuts than does PVD processes. Formation of tantalum-containing films from CVD or ALD processes using TaCl5 as a precursor may require as many as three treatment cycles using various radial based chemistries (e.g., atomic hydrogen or atomic nitrogen) to form tantalum materials. Processes using TaCl5 may also suffer from chlorine contaminants within the tantalum material. While metal-organic tantalum precursors may be used to form tantalum materials containing no chlorine contaminants, the deposited materials may suffer with the undesirable characteristic of a high carbon content. Other metal materials to be deposited for metal gate electrodes have experienced similar difficulties as the deposition of tantalum.
Therefore, there is a need for a process to deposit metal-containing materials on a substrate, including as a metal gate electrode as well as a barrier layer.